1. Field of the Invention
The present invention relates to a magnetic head and, more particularly, to a magnetic head having a magnetic gap sandwiched between magnetic materials having a high saturation magnetic flux density and a reinforcing block.
2. Related Background Art
A so-called MIG (Metal in Gap) head is known and is commercially available as a magnetic head suitable for a high coercive force magnetic medium such as a metal coating tape or a metal deposition tape.
The MIG head has a structure such that a material having a high permeability such as ferrite is used for most of a core, and a magnetic pole distal end portion near a gap is formed of a high saturation magnetic flux density, i.e., an alloy magnetic material such as permalloy, Sendust, amorphous, or the like. Two typical MIG heads are known. In an MIG head of one type, a boundary between a metal magnetic material and ferrite on a slide surface is parallel to an operation gap (the head of this type will be referred to as a P type head hereinafter, and is disclosed in, e.g., Japanese Laid-Open Patent Gazette No. 140708/1976). In an MIG head of the other type, the boundary is not parallel to the operation gap to define an azimuth (the head of this type will be referred to as an A type head hereinafter, and is disclosed in, e.g., Japanese Laid-Open Patent Gazette Nos. 96013/1979 and 32107/1985, and the like). The A type MIG head has been put into practical use to date.
In the MIG head as described above, the operation magnetic gap is formed by a so-called butt process. A head in which the operation gap is formed by the conventional butt process often involves a variation in gap width, and as a result, large variations in the characteristics of heads is caused. In order to eliminate the variations, an MIG head in which a gap is formed without the butt process is also proposed. In a head of this type, an insulating film serving as a gap material as a magnetic gap is formed on a metal magnetic film, and a metal magnetic film is formed on the insulating film.
As MIG heads including no butt process, an A type head is disclosed in Japanese Laid-Open Patent Gazette No. 173714/1985, and a P type head is disclosed in Japanese Patent Application No. 187486/1985 filed by the present applicant.
FIGS. 1A and 1B are perspective views showing conventional MIG heads including no butt process. A block 2 is formed of a high permeability magnetic material such as ferrite. A first magnetic metal film 4 comprises a magnetic metal having a high saturation magnetic flux density such as Sendust. A nonmagnetic film 6 of a nonmagnetic material such as SiO.sub.2 is deposited on the first magnetic metal film 4. A second magnetic metal film 8 is deposited on the nonmagnetic film 6. Nonmagnetic materials 10 and 14 such as glass are respectively deposited on the first and second magnetic metal films 4 and 8. A winding window 12 is formed between the nonmagnetic film 6 and the nonmagnetic material 10.
In the head of FIG. 1A, a nonmagnetic protection plate 16 serving as a reinforcing block is joined to the second magnetic metal film 8 by, e.g., glass welding. In the head of FIG. 1B, a nonmagnetic material 18 and a high permeability magnetic material 20 are joined to obtain a reinforcing block.
In the conventional magnetic head shown in FIG. 1A, a second magnetic pole is constituted by only the second magnetic metal film 8. Therefore, reluctance is high, and satisfactory electromagnetic conversion characteristics cannot be obtained.
In the magnetic head shown in FIG. 1B, it is preferable that a portion of the nonmagnetic material 18 facing the second magnetic metal film is small. However, if the portion of the nonmagnetic material becomes small in the reinforcing block, the high permeability magnetic material 18 is exposed due to chamferring of the head and wear, as shown in FIG. 1B. As a result, a dummy gap is undesirably formed between the high permeability magnetic material 20 and the second magnetic metal film 8, and a ripple is caused in frequency characteristics.
However, if the proportion of the nonmagnetic material 18 in the reinforcing block is increased, a noticeable improvement in electromagnetic conversion characteristics cannot be expected for the magnetic head shown in FIG. 1A.